Agricultural harvesters, such as agricultural combines, are designed to travel through agricultural fields harvesting crops. Agricultural combines receive crop severed from the ground and convey it to threshing, separating and cleaning devices within the agricultural combine.
In a typical arrangement, the agricultural harvesting head severs the crop from the ground and conveys it to the central region of the harvesting head. It is then conveyed rearward into a central and forwardly opening aperture in the front of the agricultural combine proper.
A reciprocating knife extends is fixed to the frame of the agricultural harvesting head and extends across the entire lower leading edge of the agricultural harvesting head. The reciprocating knife is supported on the forward ends of elongate arms that are pivotally coupled to the frame at their rear ends. The arms can pick it up and down independently of each other, thereby permitting the reciprocating knife to flex and also pivot up and down as it follows the contours of the ground during harvesting.
In this manner, the reciprocating knife can closely follow the contours of the ground as it undulates and sever the crops immediately adjacent to the ground.
The closer the reciprocating knife gets to the surface of the ground, the more likely it is to dig into the ground. When the reciprocating knife digs into the ground, it causes the arms to be pulled downward and bury the reciprocating knife in the earth. This can cause significant damage to the knife, the arms, and the agricultural harvesting head, generally.
US 20030074876 A1 discloses a crop harvesting header for mounting on a propulsion vehicle such as a swather, tractor or combine harvester includes a main frame structure supporting a crop receiving table with a cutter bar across a front of the table and side drapers on the table for moving the cut crop toward a discharge location of the header. The frame is divided into a central frame portion and two separate wing frame portions each arranged for pivotal movement relative to the central portion about a pivot axis extending in a plane parallel to the forward direction and intersecting the cutter bar so that, as the wing frame portions pivot, the cutter bar flexes in the area adjacent the respective pivot axis over a small angle of the order of 4 degrees to maintain the cutter bar following the ground. The central frame portion is mounted on two spring arms for upward and twisting floating movement such that the total downward force on the ground, from that part of the weight of all of the portions of the header which is unsupported, can be varied by moving the support to change the total pressure of the header on the ground. The wing frame portions are connected to the central frame portion by interconnecting linkages which transfer weight from the wing frame portions to the springs of the central portion each including a respective balance beam arranged to balance the lifting force from the spring with the downward forces from the center portion and wing frame portion such that the downward force on a skid plate of each portion on the ground varies automatically as the total downward force is varied. A bottom stop is arranged with a balance system which holds the cutter bar straight when the header is raised.
EP 2374344 discloses a flexible cutter bar header (22) for an agricultural plant cutting machine (20), that includes a plurality of elongate, telescoping support arms (32) pivotally connected to a floor (40) of the header and supporting a flexible cutter bar (24) for upward and downward (A), and fore and aft (B) movements relative thereto, apparatus (50, 52) extending between at least some of the support arms (32) configured and operable for controlling the telescoping thereof substantially uniformly, and a preload adjusting system (26) configured and operable for applying a preload force against the cutter bar (24) through the support arms (32) in a manner to automatically increase as the support arms (32) telescopically increase in length, and automatically decrease as the support arms (32) telescopically decrease in length.
U.S. Pat. No. 6,250,055 discloses a mower-conditioner that includes a header suspended from a mobile, main transverse frame by a pair of lower links, a single upper link and a pair of counterbalance springs. The upper link incorporates a threaded spindle to which a crank is coupled for changing the effective length of the upper link which extends between respective bearings carried by the main frame and the header and in this way pivots the header about the horizontal transverse axis defined by the bearings at the forward ends of the lower links so as to change the cutting angle of the cutter bar incorporated in the header. The upper link is mounted for sliding through the bearing carried by the header so as to permit the header to pivot upwardly about the axis in response to the cutter bar coming into contact with an obstacle during cutting operation. A coil compression spring is received on the upper link and biases it to its full effective length, the spring acting to cushion any impact of the cutter bar with an obstacle tending to tilt the header and acting to return the header to its original position once the obstacle is passed. Counterbalance springs are coupled between opposite ends of the main frame and opposite sides of the header, the springs being substantially vertically oriented with their lower ends coupled close to the bearings at the fronts of the lower links which bearings are in turn displaced only a short horizontal distance from the center of gravity of the header so as to minimize the moments about the bearings due to the weight of the header and the force of the counterbalance springs.
What is needed is an agricultural harvesting head with floating arms and reciprocating knife that is less likely to dig deeply into the ground when the knife engages the ground. What is also needed is an agricultural harvesting head with floating arms and reciprocating knife that tend to lift the reciprocating knife upward whenever the knife starts to dig into the ground.
It is an object of this invention to provide such an arrangement.